How to turn on controller with very low battery voltage

I have a solar system that powers an off-the-grid cabin. When we arrived this weekend there was no power. No sign of life at the inverter or controller. I'm working with limited tools (and experience) here, but I do have a VOM and I'm showing 6V at the 48V battery pack. I'm getting 80V from the solar panel. Upon further inspection I noticed that the switch/breaker on the side of the DC Disconnect box was off. This switch is in-line between the positive line from the solar panel and the Morningstar TS-45 controller which needs a minimum of 9V to turn on.

The theory I'm working on is that the last people here inadvertently flipped the switch off, which shutoff solar power to the controller, which stopped charging the batteries and when the batteries drained to 9V the controller shut everything down.

So how do I get the batteries up to a minimum of 9V so the controller will turn on and feed the solar power to the batteries that hopefully aren't damaged.

Is there a way to reset or trick the controller into turning on at the low voltage?

Can I take the power lead directly from the solar panel (80V) and connect it to the batteries to charge them past 9V?

I thought about wiring two of the 6V batteries in series and charging them with my truck and then reconnecting them to the 8 pack.

I would appreciate any ideas or past experiences.

Thanks, Jim

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Comments

6 volts, yikes! If there's anything left of those poor batteries, I would hook the panels directly to them and hope for the best. Remember, all a charge controller does is prevent overcharging and it appears that you're a long way for that to occur.And if they DO come back up, then be sure to reinstall the charge controller.

Switch the PV off, jumper the Controller input to the output (bypassing the controller) and switch the PV back on. You are now charging at whatever amps the PV runs at, not your MPPT rate. When the battery is able to wake the controller, pull the jumper off and the controller is now running the show, and will start the MPPT process and really boost the charge

So I'm assuming you know how to do this stuff safely and not arc weld your screwdriver into the slot. This is big time stuff, not wiring a fog light into a car.Shut the breakers and switches off first.

The longer the batteries have been depleted to such low voltage, the less likely they'll recover, don't have high expectations, that way you won't set yor self up for dissapointment, it's a long shot at best, AGM would probably never recover, flooded can take equalization and water treatment if needed, a long energy and time consuming process. Not trying to be negative just realistic, the tell tale signs of cronic sulfation will be a rapid climb in voltage with very little current and a rapid decline in voltage once the charging source is removed and or a load is applied.

The application of 80V to the bank may wake up the controller, unconventional to,say the least, good luck with your endeavors.

Thanks again for the comments and help. Got the voltage up to 12V and reconnected the controller. The controller came on and is currently doing it's job. I'll inspect the batteries carefully as the day progresses.

I had a similar situation a number of years ago (snow covered panels). Fortunately the electrolyte hadn't frozen solid (just sort of slushy).

Rather than jumping high string voltage direct to batteries (100+ volts scares me, and should scare you to), I hooked up a normal 12v car charger powered by a portable generator to 2 of the 6v batteries. This got bank voltage up enough to boot the charge controllers and inverter/chargers fairly quickly. IIRC, by the time I got the arrays cleared the controllers had come online.

Double check the battery bus voltage... Many controllers are configured to assume (guess) the battery bank voltage by measuring the present bus voltage... I.e., your bank at 12 volts may cause the controller to only charge to 14.8 volts... You might need >~35 volts on the battery bus to set the controller to 48 volt battery bank (or, if your battery bus voltage is configured with a DIP switch, you should be OK).

The breaker that flipped off... Is that a simple breaker (one or two breakers).... Or is it one of those "ground fault" breakers that has 2x normal breakers (say 60 amps) and one 1 amp breaker between system ground and "green wire" safety ground?

If this is a ground fault breaker, you may have some other electrical issue in the system (animal chewed through insulation, rain water in J-Box, etc.) that caused a short circuit to earth ground in the system which tripped the breaker.

@Estragon This is exactly what I did. I remembered I had a 12V Battery Tender up here, so I hooked up two of the 6V in series away from the full bank, cranked up an old 110 generator and let Iit run. Once I had 12V I added those two back to the bank of eight and the controller saw enough voltage to start.

@BB. The switch that was off doesn't look like a standard house breaker. It is single throw/single pole 60A. In-line on the power wire from the solar panel to the controller. One wire in, one wire out. I agree that it could've been a system fault and it did it's job, or it was accidentally switched off by the last person here.

I didn't bother removing a pair of 6v batteries from the 48v string, just tapped a 12v segment to charge. Not something I'd want to do regularly, but at the time I figured it was better than messing about with (pretty cold) bolts, etc. Can't recall if I switched between different 12v segments at first to try to get something remotely like a balanced initial charge into each segment.

LBCO is generally set to protect the attached equipment, not the bank. Not much power from LBCO to dead, so it doesn't take a lot to get from dead to LBCO.

I wanted to follow up and close this out now that I've had a chance to get back up to the cabin. Everything has been up and working since the day I found the batteries practically dead. Apparently someone, probably my wife but I don't want to get in too much trouble , hit the breaker switch on the DC Disconnect box. Charging two of the batteries using a 12v automotive Battery Tender gave me enough voltage to meet the controller minimum and get it to fire up. I'm fabricating a hinged cover and posting a note next to the switch. We'll see how the batteries do long term, but as of right now it looks like we dodged a bullet.

CleanSpeed, can you tell us a bit more about your solar array (Vmp/Imp, number of panels, series x parallel strings, etc.).

Also, is the TS-45 an MPPT or PWM controller (TS-45; PWM or TS-MPPT-45 an MPPT type controller)?

I guess you are in the Phoenix area of Arizona?

-Bill

PS: A 60 Amp breaker should not pop with a 45 Amp charge controller and the proper array configuration...

If you have friends and others over while you are not there--Perhaps some good labeling (turn this off when you leave, These switches must be on at all times--Call me if you have questions).

Best wishes for your battery bank...

Bill,

The cabin is NW of Flagstaff, AZ. Not too far from Phoenix.

The TS-45 is a PWM controller. We are running eight Schott SAPC-165 panels, I believe four in series but I'd have to look next time. The system was put in place in 2000 and we bought the cabin in 2011. It's been a fun learning curve.

With a PWM controller, they would not support a 12 volt battery bank (efficiently). 1x panel "in series" would charge a 24 volt battery bank, and 2x in series would support a 48 volt battery bank with a PWM controller.